Flavins: Photochemistry and Photobiology (Comprehensive Series in Photochemical & Photobiological Sciences, Band 6) - Hardcover

Hardcover

ISBN 10: 0854043314 ISBN 13: 9780854043316

Verlag: Royal Society of Chemistry, 2007

Inhaltsangabe

Flavins and flavoproteins are a widely investigated and highly versatile group of compounds. Participation of these compounds in photochemistry and photobiology processes are of particular importance in the fields of biology, chemistry and medicine. Written by leading experts in the field each section of the book includes a historical overview of the subject, state of the art developments and future perspectives. Flavins: Photochemistry and Photobiology begins with the properties and applications of flavins, including their photochemistry in aqueous and organic solutions. Subsequent sections discuss riboflavin as a visible light sensitizer in the photo degradation of drugs, antiviral and antibacterial effects, the role of flavins in light induced toxicity and blue light initiated DNA repair by photolyase. Finally there are sections on the flavin based photoreceptors in plants, bacteria and eukaryotic photosynthetic flagelettes. This book brings together leading experts with a unique interdisciplinary emphasis, to provide an authoritative resource on flavins and their role in photochemistry and photobiology.

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Flavins and flavoproteins are a widely investigated and highly versatile group of compounds. Participation of these compounds in photochemistry and photobiology processes are of particular importance in the fields of biology, chemistry and medicine.

Written by leading experts in the field each section of the book includes a historical overview of the subject, state of the art developments and future perspectives. Flavins: Photochemistry and Photobiology begins with the properties and applications of flavins, including their photochemistry in aqueous and organic solutions. Subsequent sections discuss riboflavin as a visible light sensitizer in the photo degradation of drugs, antiviral and antibacterial effects, the role of flavins in light induced toxicity and blue light initiated DNA repair by photolyase. Finally there are sections on the flavin based photoreceptors in plants, bacteria and eukaryotic photosynthetic flagelettes.

This book brings together leading experts with a unique interdisciplinary emphasis, to provide an authoritative resource on flavins and their role in photochemistry and photobiology.

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Flavins

Photochemistry and Photobiology

By Eduardo Silva, Ana M. Edwards

The Royal Society of Chemistry

Copyright © 2006 European Society for Photobiology
All rights reserved.

ISBN: 978-0-85404-331-6

Contents

Chapter 1 General Properties of Flavins Ana M. Edwards, 1, 
Chapter 2 Photochemistry of Flavins in Aqueous and Organic Solvents Iqbal Ahmad and Faiyaz H.M. Vaid, 13, 
Chapter 3 Excited States Interaction of Flavins with Amines: Application to the Initiation of Vinyl Polymerization María V. Encinas and Carlos M. Previtali, 41, 
Chapter 4 Riboflavin as a Visible-Light-Sensitiser in the Aerobic Photodegradation of Ophthalmic and Sympathomimetic Drugs Norman A. García, Susana N. Criado and Walter A. Massad, 61, 
Chapter 5 The Antiviral and Antibacterial Properties of Riboflavin and Light: Applications To Blood Safety and Transfusion Medicine Raymond P. Goodrich, Richard A. Edrich, Laura L. Goodrich, Cynthia A. Scott, Keith J. Manica, Dennis J. Hlavinka, Nick A. Hovenga, Eric T. Hansen, Deanna Gampp, Shawn D. Keil, Denise I. Gilmour, Junzhi Li, Christopher B. Martin and Matthew S. Platz, 83, 
Chapter 6 Light-Induced Flavin Toxicity Ana M. Edwards, 115, 
Chapter 7 Photoinduced Processes in the Eye Lens: Do Flavins Really Play a Role? Eduardo Silva and Frank H. Quina, 131, 
Chapter 8 Blue Light-Initiated DNA Repair by Photolyase Christopher W.M. Kay, Adelbert Bacher, Markus Fischer, Gerald Richter, Erik Schleicher and Stefan Weber, 151, 
Chapter 9 Flavin-Based Photoreceptors in Plants Winslow R. Briggs, 183, 
Chapter 10 Flavin-Based Photoreceptors in Bacteria Aba Losi, 217, 
Chapter 11 Photoactivated adenylyl cyclase (PAC), the photoreceptor flavoprotein with intrinsic effector function mediating euglenoid photomovements Mineo Iseki, Shigeru Matsunaga, Akio Murakami and Masakatsu Watanabe, 271, 
Chapter 12 Mechanisms of Light Activation in Flavin-Binding Photoreceptors John T.M. Kennis and Maxime T.A. Alexandre, 287, 
Subject Index, 321, 

CHAPTER 1

General Properties of Flavins

ANA M. EDWARDS

Biological Chemistry Laboratory, Faculty of Chemistry, Pontificial Universidad Católica de Chile Casilla 306, Santiago, 6091144, Chile

1.1. Introduction 1
1.2. Properties of Flavins 3
1.3. Classification of Flavoproteins 5
Acknowledgements 10
References 10

Abstract

The general properties of flavins in free solution and when bound to flavoproteins as cofactors are analysed. The extremely high chemical versatility of flavins is reflected in the remarkable versatility of flavoproteins, when considered as a whole. However, each flavoprotein is also characterized by a strict specificity, thus implying that one of the most important roles of the protein component is to limit the wide range of possible flavin–protein interactions to those beneficial to the reaction to be catalysed. Many attempts have been made to achieve a rational classification of flavoproteins, depending on their different properties. However, when general classifications are based on the different possible catalytic mechanisms, in most cases there is uncertainty, owing to the wide range of reaction mechanisms potentially available to the flavin cofactor. Despite the significant accumulation of information in recent years on catalysis, biomimetics and structural studies, the factors that determine the specificity of flavoproteins are still poorly understood.

1.1. Introduction

The yellow-coloured compounds with the basic structure of 7,8-dimethyl-10 -alkylisoalloxazine are generally termed as flavins. Flavins are ubiquitous in nature, and they take part in many biochemical reactions as coenzymes and photoreceptors. Riboflavin, the precursor of all the biologically important flavins, was first reported as lactochrome, a bright yellow pigment isolated from cow milk in 1879. Later, in the late 1920s and early 1930s, yellow pigments with bright greenish fluorescence were isolated from different sources, and they were named as lactoflavin, ovoflavin, etc., indicating the source from which they had been isolated. Concomitantly, it was recognized that the yellow pigment was a constituent of the vitamin B complex. Two important groups determined the structure and proved it by chemical synthesis. The name riboflavin (RF) was given to the compound; it derives from the ribityl side chain and from the yellow-conjugated ring system (see Figure 1).

There is a broad distribution of flavins in tissues, but little is present as free RF. The majority is found in flavocoenzymes, mainly as flavin adenine dinucleotide (FAD), and in lesser amounts as flavin mononucleotide (FMN), the common name of riboflavin-5'-phosphate, despite the known fact that RF is not a real nucleoside because the linkage between the ribityl chain and the N10 the flavin is not glycosidic; therefore, FMN and FAD are not real nucleotides. The structures are shown in Figure 1.

Since the pioneer study of Theorell, who demonstrated in 1935 that the biochemical basis for the necessity of RF as a vitamin is its role as precursor of the FMN cofactor in enzyme catalysis (coenzyme), and those by Krebs and Warburg who showed its role as precursor of FAD cofactors, hundreds of flavoprotein enzymes have been known, and new ones are reported every year. Most of them contain non-covalent-bound FAD or FMN, and are specific for binding either of the two flavin forms as nature initially provided them with. Nowadays, there are many flavoproteins crystal structures known, which reveals that the majority of the flavin-protein interactions are with the N-10 ribityl side chain of FMN or FAD. A recent study on the sequence-structure relationship in 32 families of FAD-containing proteins, showed that in every case the pyrophosphate moiety binds to the most strongly conserved sequence motif, suggesting that pyrophosphate binding is a significant component of molecular recognition.

1.2 Properties of Flavins

The redox potential for the two electron reduction of the flavin is about -200 mV. However, this value can greatly vary in flavoproteins, due to the crucial role of the protein environment in the properties of flavins, spanning a range from approximately -400 mV to +60 mV. In general, the proximity of a positive charge is believed to increase the redox potential and a negative charge or a hydrophobic environment are expected to lower it. A few flavoenzymes have a covalent-bound FAD molecule, and site-directed mutagenesis studies suggest that the covalent interaction could increase the oxidative power of the flavin.

Since the discovery and characterization of RF and its derivatives FMN and FAD, they have been recognized by their ability of participate in both one- and two-electron transfer processes. This means that flavin molecules can exist in three different redox states: oxidized, one-electron reduced (semiquinone) and two-electron reduced states. Therefore, they can participate in redox reactions as either one- and two-electron mediator making the flavoenzymes very versatile in terms of substrate and type of catalysed reactions. This is a major reason for the ubiquity of flavin-dependent enzymes in biological systems. Flavins have the potential for transfer of single electrons, of hydrogen atoms and of hydride ions. Therefore, they can participate in redox reactions as either one- and two-electron mediator making the flavoenzymes very versatile in terms of substrate and type of reactions, which is a major reason for the...

Details zur Ausgabe

• Verlag: Royal Society of Chemistry
• Erscheinungsdatum: 2007
• Sprache: Englisch
• ISBN 10: 0854043314
• ISBN 13: 9780854043316
• Einband: Gebundene Ausgabe
• Anzahl der Seiten: 340
• Herausgeber: Silva Eduardo, Edwards Ana M
• Kontakt zum Hersteller: Nicht verfügbar
• Verantwortliche Person: GPSR Kontakt; gpsr@libri.de; ; Friedensallee 273; Hamburg; 22763; Deutschland